Heat and light stabilized vinyl resins and compositions thereof



Patented May 27, 1952 HEAT STHBEIZED VINYL RESINS COMPOSITIONS THERE- James Harding; Bound Brook, N. 1., assignor to Union'Carbideairtl CarboHCorpo'ration'; a cor= porationof Ne-WYork NoDi-awing; Application-March 24; 1950,

v 3 Seria1-No.151;8-27

THis" invention relates "to the Stabilization of vinyllresinsicontaining;combined"chlorineyfrom the, degradation efiect's" of exposure wheat and light? v I Vinyl" chlorideresins can be directly-prepared by the" individual" polymerization of vinyl chlo ri dem'onomer or by 'copolymerization witira none halogen containing"vinyl'monomer' suchasvinyl acetate. More particularly, the=inventiorriscon cerned with the stabilization of vinyl chloridevinyl acetate copolymer resins sucha's are' 'de sci ibeill in U. S. Patent No. 1,935,577 to Reid.

. It iswellknown that .vi'nylchloride resiriseate highly sensitive. to. the" effectof heat; particu larly. heat of the degree requiredto soften-the resins allowing them to be shaped into a desired form as by molding, pressing or extruding: Theefiect of heat-on the normally colorlessjtransparency of these vinyl resins is to darken and eventually opacity the resins. The color change proceeds' through: shades of yellow, .deepens"tc"-ambers andbrownand finally becomes a blacliened char.

The effect of exposing vinyl chloride resins to sunlightor artificiallight'of'which a substantial" amount is in the' ultra=violet regionisals'o one, of discoloration although 'the:ratei of changeis much slower thanwith heat discoloration. Moreover, the color change isless-drastic and is prin cipally observed in the developmentof brown effective in stabilizing chlorine-containing vinyl" resinsagainst expcsure to heat;-

for many applications oftliese-vinyl resins;- den'ot impart adequate resistance to discoloration by sunlight. On the other hand, zinc or cadmium salts are known to have good lig'ht stabilizing properties. but-are practically worthl'ss 'for heat s tabi liz'a tiorrs resin is not always practical-because of interfer ingefiectsb'y-fone stabilizer on the other, 're

suitingi'n either pc'orerheat or color stability than would be normally obtainedin the absence- For:

expedient of' 'empl'oyingboth a known heat} stabilizer and a known light stabilizer '"in a vinyl Glainfsi (Cl. 260-457 of 'th'esecond' stabilizer; Furthermore; a mixtureof stabilizers may destroy the" normaltraris-- parency o'ffthes'e vinyl resins and yield cloudymr op'aque mixtures due to theirin'compatibi-lity with" ea'chbther. orwith the; vinyl resins; v

One of the objects-of the present invention-is the conjoint heat and light stabilization of *vinyl chldr'ide'polymers'or copolym'ers; V

Anotherobj ct is"the' 'heat and light stabili'za tion" 'ofthesevinyl resins with retention of i'the'ir normal transparency: 7

These and other objects as will be apparent areattained'by'incorpcrating in vinyl chlorideresins an ade'quat'efcontentof a tins'alt of anorganic carboxylic acid and from 0;5'*to" 1010'- parts by weight; per 100 parts of resin, of 'a' neutral 'or basic" substantially water in'solubl'e "salt of mag nesium and an inorganic acid such as carbonic acid-ortho or meta silicic acid, or a phosphoric acid such as ortho phosphoric acid or pyro phosphoric acid. Either the anyhdrous or hydrous forms of these salts may be employed.

The magnesium salts, as defined above, due to their water-insolubility, are substantially immune to leaching by water and hence are retainedin the vinyl resin when it is subjected to salts-are finely dispersed in the vinyl chloride resins in the amount required for color stabilization, their presence is not readily detected by unaided normal vision when the resin is in sheet form of less than 0.50 inch.

Among the specific magnesium salts having utility for the purposes of this invention are the following:

Sepidlite,2MgO 3SiOz 2HiO.'

Other magnesium salts having a refractive index outside of the preferred range of 1.50 to 1.54 when employed in optimum amounts for light stabilization tend to opacify the colorless vinyl chloride resins. Such salts include anisotropic varieties of anhydrous magnesium carbonate having a refractive index of 1.717 and 1.51; the silicates such as talc having a refractive index of 1.589 and forsterite having a refractive index of 1.651.

The tin salts of organic carboxylic salts which are useful in conjunction with the magnesium salts for conjoint light and heat stabilization are any of the tin salts described and contemplated by the aforementioned Yngve Patent 2,307,092 and the Quattlebaum et al. Patent 2,307,157. Specific representatives of such salts are dibutyl tin diacetate, dibutyl tin dioleate, diphenyl tin distearate, dibutyl tin dilaureate, dibutyl tin maleate, dibutyl tin fumarate and tri-(dibutyl tin) diaconitate.

The utility of the two types of stabilizers (inorganic magnesium salt and organic tin salt) in vinyl resins containing bound chlorine was practically determined by testing vinyl resin compositions containing various amounts of the stabilizers. Two types of test procedures were used to evaluate the performance of the compositions.

One test procedure determined heat-stability spots have become so numerous and large as to cover the major portion of the sample. The duration of exposure time to observable failure is reported in sun hours. By the term sun hours, there is meant the time during which the sun intensity exceeds 0.823 gram calories per square centimeter per minute, as measured by an Epply pyrheliometer. At the above location, there are on the average 130 sun hours per month or 1500 per year.

The superiority of the joint presence of the two types of stabilizers in vinyl chloride polymers over either stabilizer alone, or of tin salts in admixture with salts of metals other than magnesium is clearly evident from inspection of the data herewith submitted in tabular form. To reduce the variables to a minimum, for comparative analysis, the tests hereinafter set forth in Tables I and II were made with a specific vinyl chloride polymer, namely a copolymer of vinyl chloride and vinyl acetate having the approximate composition by weight of 96% vinyl chloride and 4% vinyl acetate and an intrinsic viscosity in the range 0.925 to 1.007 when measured in nitrobenzene. Test samples were prepared by hot milling at about 130-150 C. compositions having the following base formula, all parts or percentages being by weight.

. Parts on 0.040 inch thick samples prepared by hotn milling the vinyl resin and the stabilizers to form g f vmyl acetate copolymer 6O 5 an intimate dispersion. Such samples were ".T placed in an oven thermostatically controlled to Dloctyl phphala'te .(plasmclzer) Steanc acid (lubricant) 0.5 a constant temperature of 158 C. At half hour Tin salt (heat Stabilizer) 0 0 to 3 0 intervals, a sample was removed, and the c an 35 Magnesium salt of color, if any, was measured on an integrating Table I Heat Stabilization, per cent light trans Light Stabilizamission after heat- Sample Heat Stabilizer Light Stabilizer 32 3 :3 12 gif gg ffi failure A 2.0% dibutyltin None 750 80 62 5 dilaurate. B do 1%basicmagnc- Slight spot- 80 55 38 i2 situm carbontingatl,500. 9. B. C 1.0%dibutyltin None 750 82 78 78 72 maleate. D do 1% basicmagne- Slight spot- 82 80 80 79 situm carbontingatl,500.

8 e. E do 1.0% trimagne No change at 80 79 79 sium phos- 1,000.

hate. l: .do 1.0%magncsium No change at 78 57 43 10 silicate. 750. G 1.5%dibutyltin None... 500 5O 10 dilaurate. H do 1.0%megnesium 750 77 35 9 silicate. 1 I do 1.0% trimagne- No change at 84 72 10 slum phos- 1,000. photo.

at 1.5 hours.

The trimagnesium phosphate used in the specific samples had the formula Mga (P04) 2.5H2O

This eifect isiconsidered; unique that: other known stabilizers forrvinyl:clrloridefiresins which impart resistance :to. sunliglit; such as Fth'e-i salts of zinc or cadmium detrimentally affect the heat stability valuesnormally to be expected from the presence of an organic tin salt.

On the othenh'and the" magnesium salts in the presence of other; conventional heat-stabilizers such as basic lead silicate ordi-sodium+monohydrogen phosphate exhibit anomalous behavior. In some cases they decrease the "vinyl chloride polymer s normal resistance:try-sunlight, in 'other they behave practically"'asfiinert substances;-land atbest impart only. aslightincrease in the, poly:- mers resistance.tosurrlight; "drin general s'ig nifibantly-impairthelresistance toheatb In Table II there is reported the light and heatstability properties of vinyl chloride resin com positions containing various magnesium salts as light stabilizer and a conventional heat stabilizer other than a tin salt. The samples were made with the same vinyl resin, lubricant and plasticizer, and in the same manner as described for the samples reported in Table I.

Vinyl resins containing bou-nd:. cli'lenin'e andzthei twd .stabilizers comprising an organic .ttn'isal t and suitable? :magnesiumvsa'ltimayz ib'a 'compnun dede'in conventional manner with fillers, lubricants, pigments, and plasticizers in the formulation of molding compounds, extrusion compounds, coatings and adhesives exhibiting superior resistance to the eifects of heat and light.

What is claimed is:

1. Resinous composition comprising a vinyl Table II Heat Stabilization, per- Lilght Stabicent llilghg trantsiilgg sun Sam Heat Light lzatlon, a ter ea nga ple Stabilizer Stabilizer g f ij g ldmted failure a .l 2% basic lead None 500 78 78 77 76 silicate. K do 1% trimagnesi- 500 55 50 40 um phosphate. L do 1% magnesium 250 62 40 38 silicate. M 3% proprietary None 500 70 62 58 product by analysis 60% di-sodium mono-hydrogen phosphate, 40% inert filler. N.- do 1% trimagnesi- 750 58 53 45 umphosphate. O .do 1% magnesium 750 57 18 9 silicate.

1 1.5 hours.

Inspection of Table II shows that the various magnesium salts exhibit at most a neutral and occasionally an injurious effect with respect to the heat-stability imparted by the conventional heat-stabilizers. The light stability results reveal anomalous results, in one instance (sample L) a decidedly poorer value was obtained. At best, however, color failure was evident in all samples after 750 hours of sun exposure. In contrast thereto the magnesium salts in combination with tin salts of organic carboxylic acids consistently exhibited superior light stabilization, including values up to 1500 hours before visible changes occurred.

The stabilizing agents comprising the described tin salts and magnesium salts may be incorporated with vinyl resins containing bound chlorine by various methods well known to the art, including milling, or by adding the stabilizer to solutions of the resins in volatile solvents, and subsequently removing the solvent as by evaporation.

The quantity of tin salt ordinarily required for effective heat stabilization ranges from about 0.5 to 5.0 per cent by weight of the vinyl resin, with about 1 to 2 per cent generally yielding optimum results with respect to cost of stabilizer versus stabilization effect. The magnesium salts are and probably will be considerably cheaper than the tin salts and hence can be economically as a light-stabilizer therefor basic magnesium carbonate.

3. Resinous composition comprising a vinyl chloride-vinyl acetate copolymer resin and dispersed in said resin as a heat-stabilizer therefor a hydrocarbon tin salt of a carboxylic acid, and as a light-stabilizer therefor trimagnesium phosphate.

4. Resinous composition comprising a vinyl chloride-vinyl acetate copolymer resin and dispersed in said resin as a heat-stabilizer dibutyl tin maleate, and as a light stabilizer basic magnesium carbonate.

5. A heat and light stabilized composition comprising a vinyl chloride resin of a refractive index between 1.51 and 1.53 and having dispersed therein a hydrocarbon tin salt of a carboxylic at about acid in amount between 0.5 and 5.0 per cent on the weight of the vinyl resin, and a magnesium salt selected from the group consisting of the phosphates, carbonates and silicates, said magnesium salt having a refractive index between 1.50 and 1.54 and being present in amount between about 0.5 and 10.0 per cent on the weight of thevinyl resin.

6. A heat and light stable composition of a vinyl chloride resin and dispersed in said resin a lightstabilizer selected from the group consisting of alkyl tin salts and aryl tin salts and a heatstabilizer of a salt of magnesium selected from the group consisting of the phosphates, carbonates and silicates.

'7. A heat and light stable composition of a vinyl chloride resin and dispersed in said resin 8 a hydrocarbon tin salt of a carboxylic acid and a salt of magnesium selected from the group consisting of the phosphates, carbonates and silicates.

5 JAMES HARDING.

REFERENCES CITED The following references are of record in the file of this patent: UNITED STATES PA'IENTS Number Name Date 2,046,986 Winkelmann July '7, 1936 r 2,307,092 Yngve Jan. 5, 1943 '15 2,307,157 Quattlebaum Jan. 5, 1943 2,364,410 Whittaker Dec. 5, 1944 

1. RESINOUS COMPOSITION COMPRISING A VINYL CHLORIDE RESIN HAVING A REFRACTIVE INDEX VALUE BETWEEN 1.51 AND 1.53 AND DISPERSED IN SAID RESIN AS A HEAT-STABILIZER THEREFOR A HYDROCARBON TIN SALT OF A CARBOXYLIC ACID, AND AS A LIGHT-STABILIZER THEREFOR A SALT OF MAGNESIUM HAVING A REFRACTIVE INDEX BETWEEN 1.50 AND 1.54 AND SELECTED FROM THE GROUP CONSISTING OF THE PHOSPHATES, CARBONATES AND SILICATES. 